arXiv subjects

Joel C. Pommerening

Publications and source records attributed to Joel C. Pommerening.

2 recordsLinked to original sources

arXiv2022

Explicit diagrammatic solution of normalised, nondegenerate Rayleigh-Schrödinger perturbation theory

We solve the coupled recurrence relations for eigenenergies and -vectors in nondegenerate Rayleigh-Schrödinger perturbation theory under the constraint that the approximate eigenvector be normalised to $1$ in every order. The series can be expressed in terms of diagrams that were first introduced by C. Bloch [Nucl. Phys. 6, 329 (1958)] for the degenerate, unnormalised case. Normalisation increases the number of terms and introduces a nontrivial dependence on the diagrams' topology to the coefficients.

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arXiv2020

What is measured when a qubit measurement is performed on a multi-qubit chip?

We study how single-qubit dispersive readout works alongside two qubit coupling. To make calculations analytically tractable, we use a simplified model which retains core characteristics of but is discretised compared to dispersive homodyne detection. We show how measurement speed and power determine what information about the qubit(s) is accessed. Specifically we find the basis the measurement is closest to projecting onto. Compared to the basis gates are applied in, this measurement basis is modified by the presence of photons in the readout resonator.

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